In radiofrequency surgery (RF surgery), a high-frequency alternate current is conducted through the human body in order to cut or coagulate tissue in a targeted manner. A general distinction is made between a monopolar application and a bipolar application of the treatment current. In a monopolar application, usually only one application electrode is provided, with a high-frequency alternate current usually being applied to the application electrode, which may, for example, be located in an electrosurgical instrument used for cutting and/or coagulating tissue. Furthermore, a large-surface neutral electrode is attached to the body of the patient. When RF current is applied, an RF voltage is applied to the application electrode and to the neutral electrode, thus closing the electric circuit across the interposed tissue. The shape of the application electrode depends on the respective field of application. The contact surface of the application electrode across which the alternate current is conducted into the tissue is relatively small, resulting in a high current density being formed in the direct environment of the application electrode and, consequently, also a great development of heat.
As the distance from the application electrode increases, the current density greatly decreases, unless there are also high current densities at other sites of the body due to considerable variations in tissue conductivity. In bipolar applications, the RF voltage is applied to two application electrodes that are located close to each other, e.g., bipolar coagulation forceps. This means that the current mainly flows through tissue located between the application electrodes. Preferably, the application electrodes are arranged on one instrument. However, often, hard to access tissue sites can only be reached and treated with difficulty, or not at all, with such instruments.
Supply devices supply the electrosurgical instruments with a suitable RF voltage and a suitable RF current, so that a problem-free treatment of the patient is possible. Desired RF current and RF voltage vary as a function of the tissue that is to be treated and also as a function of the mode of operation that is used (e.g., coagulation mode, cutting mode). Other modes of operation for different types of tissue are conceivable. Therefore, the supply device must constantly regulate the RF output voltage and/or the RF output current in order to ensure an appropriate operation of the electrosurgical instrument. Consequently, it is necessary, at times, that the operating parameters be adaptable, since the quality of the tissue that is treated with the use of an instrument changes constantly. Considering this, for example, when the conductivity of the tissue decreases, the resistance thus increases on account of the applied RF current. Conversely, untreated tissue types (e.g., fatty tissue, muscle tissue, nerve tissue) also display different resistances that must be taken into consideration in voltage or current regulation.
This regulation is desired so that the treating physician is able to safety cut and/or coagulate tissue, regardless of the type and quality of the tissue. Therefore, in order to ensure the proper functioning of the electrosurgical instrument, the supply device must control or regulate the power of the RF generator or the RF generator unit. The power that is provided in this case is usually restricted by the capacity of the generator that is being used and by the corresponding safety guidelines. Thus, it may happen that too high a power output is used without the physician noticing this. This is dangerous and can result in unwanted tissue damage. Furthermore, physicians may not be used to handling such an electrosurgical instrument because they are used to a haptic feedback (e.g., tactile feedback) when performing cutting operations.
Considering this prior art, it is the object of the disclosed embodiments to provide a supply device that allows a safe and functional operation, and facilitates the handling of an electrosurgical instrument. Furthermore, disclosed embodiments also include a corresponding RF apparatus, a method for the operation of an RF generator unit, and a method for performing an electrosurgical operation.